forked from cockroachdb/cockroach
/
batch.go
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/
batch.go
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// Copyright 2015 The Cockroach Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
// implied. See the License for the specific language governing
// permissions and limitations under the License. See the AUTHORS file
// for names of contributors.
//
// Author: Tobias Schottdorf
package kv
import (
"math/rand"
"github.com/cockroachdb/cockroach/client"
"github.com/cockroachdb/cockroach/keys"
"github.com/cockroachdb/cockroach/proto"
"github.com/cockroachdb/cockroach/util"
"golang.org/x/net/context"
)
// truncate restricts all contained requests to the given key range.
// Even on error, the returned closure must be executed; it undoes any
// truncations performed.
// First, the boundaries of the truncation are obtained: This is the
// intersection between [from,to) and the descriptor's range.
// Secondly, all requests contained in the batch are "truncated" to
// the resulting range, inserting NoopRequest appropriately to
// replace requests which are left without a key range to operate on.
// The number of non-noop requests after truncation is returned along
// with a closure which must be executed to undo the truncation, even
// in case of an error.
// TODO(tschottdorf): Consider returning a new BatchRequest, which has more
// overhead in the common case of a batch which never needs truncation but is
// less magical.
func truncate(br *proto.BatchRequest, desc *proto.RangeDescriptor, from, to proto.Key) (func(), int, error) {
if !desc.ContainsKey(from) {
from = desc.StartKey
}
if !desc.ContainsKeyRange(desc.StartKey, to) || to == nil {
to = desc.EndKey
}
truncateOne := func(args proto.Request) (bool, []func(), error) {
if _, ok := args.(*proto.NoopRequest); ok {
return true, nil, nil
}
header := args.Header()
if !proto.IsRange(args) {
if len(header.EndKey) > 0 {
return false, nil, util.Errorf("%T is not a range command, but EndKey is set", args)
}
if !desc.ContainsKey(keys.KeyAddress(header.Key)) {
return true, nil, nil
}
return false, nil, nil
}
var undo []func()
key, endKey := header.Key, header.EndKey
keyAddr, endKeyAddr := keys.KeyAddress(key), keys.KeyAddress(endKey)
if keyAddr.Less(from) {
undo = append(undo, func() { header.Key = key })
header.Key = from
keyAddr = from
}
if !endKeyAddr.Less(to) {
undo = append(undo, func() { header.EndKey = endKey })
header.EndKey = to
endKeyAddr = to
}
// Check whether the truncation has left any keys in the range. If not,
// we need to cut it out of the request.
return !keyAddr.Less(endKeyAddr), undo, nil
}
var fns []func()
gUndo := func() {
for _, f := range fns {
f()
}
}
var numNoop int
for pos, arg := range br.Requests {
omit, undo, err := truncateOne(arg.GetInner())
if omit {
numNoop++
nReq := &proto.RequestUnion{}
if !nReq.SetValue(&proto.NoopRequest{}) {
panic("RequestUnion excludes NoopRequest")
}
oReq := br.Requests[pos]
br.Requests[pos] = *nReq
posCpy := pos // for closure
undo = append(undo, func() {
br.Requests[posCpy] = oReq
})
}
fns = append(fns, undo...)
if err != nil {
return gUndo, 0, err
}
}
return gUndo, len(br.Requests) - numNoop, nil
}
// SenderFn is a function that implements a Sender.
type senderFn func(context.Context, proto.BatchRequest) (*proto.BatchResponse, error)
// SendBatch implements batch.Sender.
func (f senderFn) SendBatch(ctx context.Context, ba proto.BatchRequest) (*proto.BatchResponse, error) {
return f(ctx, ba)
}
// A ChunkingSender sends batches, subdividing them appropriately.
type chunkingSender struct {
f senderFn
}
// NewChunkingSender returns a new chunking sender which sends through the supplied
// SenderFn.
func newChunkingSender(f senderFn) client.BatchSender {
return &chunkingSender{f: f}
}
// SendBatch implements Sender.
// TODO(tschottdorf): We actually don't want to chop EndTransaction off for
// single-range requests (but that happens now since EndTransaction has the
// isAlone flag). Whether it is one or not is unknown right now (you can only
// find out after you've sent to the Range/looked up a descriptor that suggests
// that you're multi-range. In those cases, the wrapped sender should return an
// error so that we split and retry once the chunk which contains
// EndTransaction (i.e. the last one).
func (cs *chunkingSender) SendBatch(ctx context.Context, ba proto.BatchRequest) (*proto.BatchResponse, error) {
if len(ba.Requests) < 1 {
panic("empty batch")
}
// Deterministically create ClientCmdIDs for all parts of the batch if
// a CmdID is already set (otherwise, leave them empty).
var nextID func() proto.ClientCmdID
empty := proto.ClientCmdID{}
if empty == ba.CmdID {
nextID = func() proto.ClientCmdID {
return empty
}
} else {
rng := rand.New(rand.NewSource(ba.CmdID.Random))
id := ba.CmdID
nextID = func() proto.ClientCmdID {
curID := id // copy
id.Random = rng.Int63() // adjust for next call
return curID
}
}
parts := ba.Split()
var rplChunks []*proto.BatchResponse
for _, part := range parts {
ba.Requests = part
ba.CmdID = nextID()
rpl, err := cs.f(ctx, ba)
if err != nil {
return nil, err
}
// Propagate transaction from last reply to next request. The final
// update is taken and put into the response's main header.
ba.Txn.Update(rpl.Header().Txn)
rplChunks = append(rplChunks, rpl)
}
reply := rplChunks[0]
for _, rpl := range rplChunks[1:] {
reply.Responses = append(reply.Responses, rpl.Responses...)
}
reply.ResponseHeader = rplChunks[len(rplChunks)-1].ResponseHeader
reply.Txn = ba.Txn
return reply, nil
}
// prev gives the right boundary of the union of all requests which don't
// affect keys larger than the given key.
// TODO(tschottdorf): again, better on BatchRequest itself, but can't pull
// 'keys' into 'proto'.
func prev(ba proto.BatchRequest, k proto.Key) proto.Key {
candidate := proto.KeyMin
for _, union := range ba.Requests {
h := union.GetInner().Header()
addr := keys.KeyAddress(h.Key)
eAddr := keys.KeyAddress(h.EndKey)
if len(eAddr) == 0 {
// Can probably avoid having to compute Next() here if
// we're in the mood for some more complexity.
eAddr = addr.Next()
}
if !eAddr.Less(k) {
if !k.Less(addr) {
// Range contains k, so won't be able to go lower.
return k
}
// Range is disjoint from [KeyMin,k).
continue
}
// We want the largest surviving candidate.
if candidate.Less(addr) {
candidate = addr
}
}
return candidate
}
// next gives the left boundary of the union of all requests which don't
// affect keys less than the given key.
// TODO(tschottdorf): again, better on BatchRequest itself, but can't pull
// 'keys' into 'proto'.
func next(ba proto.BatchRequest, k proto.Key) proto.Key {
candidate := proto.KeyMax
for _, union := range ba.Requests {
h := union.GetInner().Header()
addr := keys.KeyAddress(h.Key)
if addr.Less(k) {
if eAddr := keys.KeyAddress(h.EndKey); k.Less(eAddr) {
// Starts below k, but continues beyond. Need to stay at k.
return k
}
// Affects only [KeyMin,k).
continue
}
// We want the smallest of the surviving candidates.
if addr.Less(candidate) {
candidate = addr
}
}
return candidate
}